Allow ResourceAction#fqname=nil to clear ae_*

[agrare]

Now that resource actions can have either embedded_automate ae_* values or a configuration_script_id it is helpful to clear the ae_* values for an existing resource action.

Ref: ManageIQ/manageiq-ui-classic#8815

[miq-bot]

Checked commit agrare@95b8e32 with ruby 2.6.10, rubocop 1.28.2, haml-lint 0.35.0, and yamllint
2 files checked, 0 offenses detected
Everything looks fine. 🍪

[Fryguy]

Backported to petrosian in commit 221864a.

commit 221864a702055f5bfd66a2c552b7bd4546e01166
Author: Jason Frey <fryguy9@gmail.com>
Date:   Wed Jul 5 13:54:22 2023 -0400

    Merge pull request #22600 from agrare/allow_fqname_eql_set_to_nil
    
    Allow `ResourceAction#fqname=nil` to clear `ae_*`
    
    (cherry picked from commit 4b5fe6070fff1f9eb4d51283f3b0ccfa786628e4)